I always turn the Bluetooth transmitter off on my PDA when flying. Saves battery life as well!
Wi-Fi is very low power compared to mobiles, and indeed is used on the Connexxion system:
http://www.80211-planet.com/news/article.php/1570531
The interesting thing is the weight factor of Ethernet cables compared to wireless, and also the cost of installation. I wonder if 802.11g (the fastest WiFi available) could be used in future to transmit TV/audio signals, negating the need for complex IFE installations?